#include <stdio.h>
#include <iostream>
int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        if(n<0||n>100)
            printf("Score is error!\n");
        if(90<=n&&100>=n)
            printf("A\n");
        if(80<=n&&89>=n)
            printf("B\n");
        if(70<=n&&79>=n)
            printf("C\n");
        if(60<=n&&69>=n)
            printf("D\n");
        if(n<60)
            printf("E\n");
    }
    return 0;
}